KR100202248B1 - Process and device for producing al-pb based bearing alloy powder - Google Patents

Abstract

Disclosed is a method and an apparatus for producing an Al-Pb-based bearing alloy powder in which Pb is homogeneously and finely distributed on an Al base.

The present invention relates to a process for producing a homogeneous molten metal by stirring a molten mixture of Al and Pb in a liquid phase to obtain a homogeneous molten metal and rapidly solidifying the homogeneous molten metal by atomizing the molten metal by spraying a high- Based bearing alloy powder.

The apparatus for producing an Al-Pb-based bearing alloy powder according to the present invention comprises a melting furnace having an outlet, an agitating device provided in the melting furnace for homogeneously mixing the molten Al and Pb, and a high-pressure gas device .

Description

Method and apparatus for manufacturing Al-Pb-based bearing alloy powder

The present invention relates to a method and an apparatus for producing an oilless Al-Pb-based bearing alloy powder, and more particularly to a method and an apparatus for producing an Al-Pb-based bearing alloy powder in which Pb is uniformly and finely distributed on an Al base will be.

In general, Cu-based alloys and Al-Sn-based alloys are widely used as bearing alloys. However, since Al-Pb-based bearings are light in weight and have excellent wear characteristics and low cost, their use is gradually increasing. Al-Pb-based bearings, which rely on imports in comparison to many demands, are economical materials and simple to manufacture, making them very easy to apply in industry. Al-Pb-based bearing alloys are used, for example, in the manufacture of bearings and bushings used in internal combustion engines of automobiles. Al and Pb exist in a liquid phase separated state due to the unbalance reaction and gravity segregation at the time of dissolving, and the difference in density between Al and Pb is about 4.2 times larger than that in the conventional casting method. Therefore, Pb particles, which are solid lubricants, It is difficult to finely distribute it. Conventionally, in order to solve such metallurgical problems caused by the unbalance reaction and gravity segregation, there have been proposed an ultrasonic vibration method in which ultrasonic waves are applied from a molten state to a solidified state, a chiller is attached to the ingot cross- A directional solidification method in which a solidified structure in which crystals grow vertically is obtained by cooling, a third element addition method in which a third element other than a desired composition is added, and a powder metallurgy method (MA) in which an Al powder and a Pb powder are mixed Al-Pb alloy was prepared. However, these methods are not only expensive to manufacture, but also can not finely and uniformly spray Pb particles in an Al matrix, resulting in poor performance as a bearing material. In addition, these conventional manufacturing methods have a problem that Pb can not employ about 20% by weight, which is the minimum Pb content required to serve as a solid lubricant. And the homogeneous lubrication layer can not be formed due to the coarsening of the Pb particles in the powder.

An object of the present invention is to provide a method for producing an Al-Pb alloy powder in which Pb is homogeneously and finely distributed on an Al base.

FIG. 1 is a schematic view of a rapid solidification device bonded to produce an Al-Pb-based bearing alloy powder according to the present invention; FIG.

FIG. 2 is a view showing the flow of molten metal during operation of the screw type stirrer of the rapid solidification device of FIG. 1; FIG.

FIG. 3 is a diagram showing micro-Vickers hardness of an Al-Pb-based alloy.

4 shows the effect of the sliding speed (sliding distance 100 m, load 2.1 Kg) on the bimamo of the extruded Al-Pb type alloy.

5 shows the effect of the sliding distance (sliding speed 2.41 m / sec, load 2.1 Kg) on the asymmetry of the extruded Al-Pb alloy.

6a to 6c are micrographs of the microstructure of the Al-Pb alloy according to the manufacturing method. FIG. 6a is a micrograph of the underlying structure of the Al-Pb alloy ingot by a general casting method, Micrographs of the microstructure of the Al-Pb alloy when quenched, and FIG. 6C is a micrograph of the microstructure of the Al-Pb alloy rapidly cooled and cooled by the gas atomization method according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

10: Bearing alloy powder manufacturing apparatus 11: Liquid homogenizing apparatus

13: Crucible 15: With electrical resistance

17: thermocouple 19: screw type stirrer

21: screw 23: drive motor

25: Orifice 31: Rapid solidification device

33: nitrogen gas supplier 35: injection nozzle

37: chamber 39: collection container

Another object of the present invention is to provide an apparatus for producing an Al-Pb alloy powder in which Pb is homogeneously and finely distributed on an Al base.

In order to achieve the above object, the present invention provides a method for producing a homogeneous molten metal by mixing molten Al and Pb in a liquid state to form a homogeneous molten metal, flowing the homogeneous molten metal, And then rapidly solidifying the molten metal by atomizing the molten metal, thereby providing an Al-Pb-based bearing alloy powder manufacturing method.

The present invention also relates to a method for producing a molten metal, comprising a melting furnace having an outlet, a stirring device for homogeneously mixing Al and Pb molten metal provided in the melting furnace, and a high-pressure gas device having an injection nozzle positioned around the outlet, The high-pressure gas is sprayed to the molten metal through the injection nozzle to atomize the molten metal, thereby rapidly solidifying the molten metal flowing out, and an Al-Pb-based bearing alloy powder manufacturing apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an apparatus 10 for manufacturing an Al-Pb-based bearing alloy powder according to an embodiment of the present invention. The Al-Pb-based bearing alloy powder production apparatus (10) comprises a liquid homogenizing device (11) for preventing segregation of the liquid specific gravity of Al and Pb and homogenizing the entire molten metal, a high-pressure homogenizer (11) for homogenizing the molten liquid, And a rapid solidification device 31 for rapid solidification cooling. When making the melt, pure Al and pure Pb are put into the crucible in ingot form. However, since Pb is a metal having a low melting point, it is volatile and it is added in an Al foil packed just before the preparation of powder to obtain an accurate composition ratio.

The liquid homogenizer 11 includes a crucible 13 for containing Al and Pb molten metal, a high-frequency electric resistance furnace 15 for surrounding the crucible and dissolving Al and Pb to keep it in a molten state, A screw type stirrer 19 for homogenizing the upper and lower portions of the molten metal and a drive motor 23 for rotating the helical screw 21 of the screw type stirrer connected to the screw type stirrer, And an orifice 25 provided at a lower portion of the crucible so that the molten metal can freely fall outwardly when opened. Since the screw 21 of the agitator 19 is spiral, when the driving motor 23 is driven to rotate, the Pb particles sinking to the bottom due to the difference in specific gravity are introduced into the screw holes So that the upper and lower portions of the molten metal are homogenized as a whole. The homogenized melt is freely dropped into the chamber 37 of the rapid solidification device 31, which will be described later, by opening the orifice 25 by a suitable means not shown in the figure.

The rapid solidification device 31 includes a nitrogen gas supply device 33 for supplying a high pressure nitrogen gas and an orifice 25 for enclosing the orifice 25 of the homogenizer 11 and supplying the nitrogen gas supplied from the nitrogen gas supply device 33 to the orifice 25. [ A chamber 37 in which the rapidly solidified alloy powder is scattered by the nitrogen gas and a collecting container 39 for collecting the rapidly solidified alloy powder, ). The collecting container 39 can be moved away from the main body of the rapid solidifying device. A solenoid valve 43 for supplying and shutting off nitrogen gas is provided in the supply passage 41 that communicates with the injection nozzle 35 from the nitrogen gas supply unit 33 and a nitrogen gas supply unit A pressure regulator 45 for regulating the pressure of the refrigerant is installed. The size of the chamber 37 is determined in consideration of the flying distance of the alloy powder solidified so that the alloy powder in rapid solidification is sufficiently cooled.

Now, a method of manufacturing the Al-Pb-based bearing alloy powder according to the present invention will be described in detail with respect to the above-described Al-Pb-based bearing alloy powder manufacturing apparatus 11.

Al-Pb-based bearing alloys vary greatly in wear characteristics depending on the content of Pb, which is a solid lubricant, and the hardness values of Al-base supporting loads are also important factors for wear characteristics of bearings. That is, the coefficient of friction of the bearing . (here, The friction coefficient, Is the shear strength, and H is the hardness)

As can be seen from the above relationship, the Pb particles that are liquefied during operation to form the solid lubricating layer can reduce the shear strength and increase the hardness value to reduce the friction coefficient. Pb particles must be finely and uniformly distributed in the powder to form a lubricating layer over the entire wear surface.

It is known in the technical field of the present invention that the Pb content should be at least 20% by weight in order for Pb to act as a solid lubricant. However, according to the present invention, it has been found that since Pb particles are uniformly and finely distributed, Pb can sufficiently serve as a solid lubricant even at a Pb content of less than 20% by weight.

As a result of the experiment, it was found that when 16 wt% of Pb was added, the most suitable lubricant layer thickness was formed. Cu, Mg, and Si may be added to strengthen the matrix. FIG. 3 is a graph showing the results when the content of Pb is 10 wt%, 16 wt% and 20 wt%, and when the content of Pb is 16 wt% and Cu, Cu-Mg and Cu-Mg- The hardness Hv of the case is shown. From the third road, it can be seen that the hardness value decreases as the content of Pb increases in the binary Al-Pb alloy, and when the Cu, Mg and Si are added to the binary Al-16Pb alloy, . 4 and 5, it can be seen that the abrasion characteristics are excellent in proportion to the hardness value because the factors determining the abrasion amount are the hardness value and the shear strength. That is, , The coefficient of friction ( ), The shear strength decreased by Pb ( ) To 0 and increase the hardness value H which is increased by addition of the alloying elements (Cu, Mg, Si). FIG. 4 shows the effect of the sliding speed (sliding distance 100 m, load 2.1 Kg) on the asymmetry of the extruded Al-Pb-based alloy. FIG. 5 shows the effect of the sliding distance (sliding speed 2.41 m / sec, load 2.1 Kg) on the bimodal of the extruded Al-Pb based alloy. Al-16Pb alloy has the best abrasion characteristics and the alloy elements (Cu, Mg, Si) are added to the Al-16Pb alloy in the binary system from the 4th and 5th roads. The hardness value increases, and accordingly, the amount of wear is reduced.

In order to overcome the metallurgical problems of Al and Pb when the Al and Pb metals are melted in the crucible 13 by the high-frequency electrical resistance furnace 15, a vacuum or inert gas atmosphere is used to control the liquid- , 1100 to 1200 And the driving motor 23 is operated to stir the molten metal by the screw type stirrer 19 to produce a homogeneous liquid phase. When this liquid phase is sprayed with a nitrogen gas having a high pressure, for example, 12 atm, supplied from the nitrogen gas supplier 33 while falling freely through the orifice 25 having a short distance, the melt flow in the liquid phase instantaneously breaks down, do.

Fine powder simultaneously with the collision of 10 ³ / sec or higher, so that a homogeneous solid phase solidified from a molten state of a homogeneous liquid phase to a finer, for example, an average particle size of 85 Of Al-Pb alloy powder is produced. As shown in the micrograph of FIG. 6c, the fine powder of almost spherical shape is a structure in which Pb is finely and uniformly distributed on an Al base. In this case, the size of the Pb particles in the powder is 0.1 to 0.3 Respectively. FIG. 6c is a micrograph of the microstructure of the Al-Pb alloy subjected to the rapid coagulation cooling by the gas spraying method according to the present invention, and FIG. 6c is a microscopic photograph of the substructure of the Al-Pb alloy ingot prepared by the general casting method. Comparing the microstructure of the microstructure of Al-Pb alloy quenched in water with water, the microstructure of Al-Pb alloy powder produced by the present invention shows much finer and homogeneous distribution of Pb on the Al base .

The Al-Pb-based alloy powder that has been cooled by gas spraying can be made into Al-Pb-based alloy bearing for various uses with high strength and high abrasion resistance through processes such as molding and sintering.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, when the Al-Pb-based alloy is dissolved in a high-frequency induction furnace in a vacuum and an inert gas atmosphere, in order to suppress segregation due to the difference in specific gravity between Al and Pb, Type stirrer, the bottom molten metal segregated can be agitated with the upper molten metal to make a homogeneous Al-Pb molten state. Pb particles are finely and homogeneously distributed by injecting high-pressure nitrogen gas and spraying the Al-Pb alloy melt, which is hardly segregated, to induce gravitational segregation, so that Al-Pb bearing alloy powder Can be manufactured. In order to rapidly cool the Al-Pb alloy molten metal, Ar gas may be used instead of nitrogen gas, but in this case, the production cost is increased. Air may also be used for mass production purposes.

Conventional techniques use various special casting methods, but they require a lot of equipment cost and a long manufacturing time. In addition, the size of the Pb particles which determine wear resistance is great and the distribution thereof is not uniform. However, by using this process, mass production is possible and the size of the Pb particles in the powder is 0.1 to 0.3 And the Al-Pb-based alloy powder is molded and sintered to produce a high-strength Al-Pb-based bearing alloy excellent in abrasion resistance.

Claims (6)

A method for producing an Al-Pb-based bearing alloy powder, comprising the steps of: mixing a molten mixture of liquid Al and Pb into a homogeneous molten metal; flowing the homogeneous molten metal; And spraying a gas to atomize the molten metal to rapidly solidify the molten alloy. The method for producing an Al-Pb based bearing alloy powder according to claim 1, wherein the content of Pb is 16% by weight. An apparatus for producing an Al-Pb-based bearing alloy powder, comprising: a melting furnace having an outlet; an agitating device provided in the melting furnace for homogenously mixing the molten liquid of Al and Pb; and an injection nozzle Wherein the molten metal is rapidly solidified by spraying a high-pressure gas to the molten metal flowing out through the outlet through the injection nozzle to atomize the molten metal, thereby rapidly solidifying the molten metal flowing out of the molten metal. . 4. The apparatus for manufacturing an Al-Pb-based bearing alloy powder according to claim 3, wherein the stirring device is provided with a spiral screw. The Al-Pb-based bearing alloy powder manufacturing apparatus according to claim 3 or 4, further comprising a chamber in which the rapidly solidifying alloy powder is scattered, and a collection container for collecting the rapidly solidified alloy powder . 5. The apparatus for producing an Al-Pb-based bearing alloy powder according to claim 3 or 4, wherein the high-pressure gas is nitrogen gas.